Investigation on building eave effect of fire-induced ejected plume from a room window and its heat flux imposing upon the facade wall

摘要

This paper investigates building eave effect of fire-induced ejected plume from a room window and its heat flux imposing upon the facade wall. Based on a 1:8 cubic model and Froude modeling, a series of reduced scale experiments are set up. The window dimensions and total heat release rate due to a room fire are changed during experiments. The eave upon the facade wall, made of noncombustible fiber board is installed horizontally above the window top, varying with different vertical heights (distance of the eave to the window top) and lengths (direction normal to the facade wall). The facade flame height is recorded by a CCD camera, while the heat fluxes imposing upon the facade wall are collected by five water-cooled heat flux gauges. Results show that the ejected flame with horizontal eave can be distinguished into the "free flame stage", the "flame horizontal spread stage" and the "flame overflow stage". The visible flame height and heat flux within the "flame overflow stage" are detailed discussed, revealing the physical mechanism of the vertical height and length of the horizontal eave effects. Finally, an implicit correlation in regarding with the visible flame height, the updated flame extension area beneath the horizontal eave as well as the vertical height of the horizontal eave to the window top is established. Taking the horizontal eave conditions into consideration, the heat flux correlation is well corrected and proposed. The results would provide theoretical basis for the fire-induced thermal protection in high buildings.